This invention relates to inkjet printers and, more particularly, to a monolithic printhead for an inkjet printer.
Inkjet printers typically have a printhead mounted on a carriage that scans back and forth across the width of a sheet of paper feeding through the printer. Ink from an ink reservoir, either on-board the carriage or external to the carriage, is fed to ink ejection chambers on the printhead. Each ink ejection chamber contains an ink ejection element, such as a heater resistor or a piezoelectric element, which is independently addressable. Energizing an ink ejection element causes a droplet of ink to be ejected through a nozzle for creating a small dot on a medium. The pattern of dots created forms an image or text.
Additional information regarding a particular printhead and inkjet printer is found in U.S. Pat. No. 5,648,806, entitled xe2x80x9cStable Substrate Structure for a Wide Swath Nozzle Array in a High Resolution Inkjet Printer,xe2x80x9d by Steven Steinfield et al., assigned to the present assignee and incorporated herein by reference.
As the resolutions and printing speeds of printheads increase to meet the demanding needs of the consumer market, new printhead manufacturing techniques and structures are required. One approach for improving the performance, ease of manufacturing, and reliability of printheads is to form the entire printhead as a monolithic structure, generally using integrated circuit fabrication techniques.
As the resolutions of the printheads increase and the size of each ink ejection chamber and nozzle grows smaller, clogging of a chamber or nozzle with an ink particle or other contaminant becomes more likely. The clogging of a chamber or nozzle degrades the quality of the image being printed. Hence, there is a need for techniques to lower the likelihood of a particle clogging a chamber or nozzle.
Described herein is a monolithic printhead formed using integrated circuit techniques. Thin film layers, including a resistive layer, are formed on a top surface of a silicon substrate. The various layers are etched to provide conductive leads to heater resistor elements. Additional layers may perform other functions such as passivation, heat sinking, and electrical isolation. Piezoelectric elements may be used instead of the resistive elements.
An orifice layer is formed on the top surface of the thin film layers to define the nozzles and ink ejection chambers. In one embodiment, a photodefinable material is used to form the orifice layer.
A trench is etched in the bottom surface of the substrate, where the etch leaves a thin silicon membrane under the ink ejection chambers.
Ink feed holes are formed through the silicon membrane, using a backside etch, so that ink may flow from an ink reservoir, into the trench, through the ink feed holes, and into associated ink ejection chambers. To reduce the likelihood of an ink particle blocking ink from entering an ink chamber, narrow ink channels are etched in the bottom surface of the thin silicon membrane leading to each of the holes such that, if an ink particle blocks an ink feed hole opening, ink can still enter the chamber by flowing within the relatively narrow channels leading into a side of the ink feed hole. Any number of channels per ink feed hole can be used.
The resulting fully integrated thermal inkjet printhead can be manufactured to a very precise tolerance since the entire structure is monolithic, meeting the needs for the next generation of printheads.